1. Field of the Invention
The present invention relates to an image processing apparatus that detects a specific area from an image, an image processing method, and a computer-readable recording device.
2. Description of the Related Art
As a technology related to the division of an image into areas, a method is disclosed in Japanese Laid-open Patent Publication No. 2009-0232962 in which an area to be discriminated in an image is divided into a target area (kidney area) and a background area by using a graph cut area division method and thus the kidney area is extracted.
The graph cut area division method is a method of dividing, as described in the following, an image into a specific area to be detected and a non-specific area that is the background of the area to be detected. First, a connected graph is created. Multiple nodes N corresponding to multiple pixels in an image and two nodes S and T, which are determination labels for each pixel and correspond to the specific area and the non-specific area, are connected via links. Each link represents by its size the probability for each pixel that the pixel is attributed to the specific area or the non-specific area. Furthermore the nodes corresponding to pixels and adjacent to each other are connected via links. Each link represents by its size the probability that the adjacent pixels are contained in the same area. Then, by cutting off the links in the connected graph, the group of nodes N is separated into a group connected to the node S and a group connected to the node T. The links are cut off such that the sum of the probability is the minimum using the max-flow min-cut theorem of graph network theory (i.e., the sum of the probability of uncut links is the maximum), thereby area division is optimized (see Y. Boykov, M. Jolly, “Interactive Graph Cuts for Optimal Boundary & Region Segmentation of Objects in N-D Images”, Proceeding of “International Conference on Computer Vision”, July 2001, vol. 1, pp. 105-112).